Apparatus and method for hydrocarbon conversion of two separate feeds



Sept. 11, 1962 P. F. SWANSON 3,053,752

. APPARATUS AND METHOD FOR HYDROCARBON CONVERSION OF TWO SEPARATE FEEDSFiled Dec. 17, 1958 HYC. PRODUCT 14 68 STEAM- A A A HYC FEED FLUE GAS 34INVENTOR. PAUL F. SWANSON ATTORNEY LAJMW AGENT United States PatentOfifice 3,053,752 Patented Sept. 11, 1962 3,053,752 APPARATUS AND METHGDFOR HYDROCARBON CONVERSION OF TWO SEPARATE FEEDS Paul F. Swanson, ShortHills, N.J., assignor to The M. W. Kellogg Company, Jersey City, N.J., acorporation of Delaware Filed Dec. 17, 1958, Ser. No. 781,072 6 Claims.(Cl. 208-78) This invention relates to an improved method and means forconverting high-boiling hydrocarbons to lower boiling hydrocarbons. Inone aspect this invention relates to the method and apparatus forefiecting cracking of hydrocarbons in stages within a single vessel toproduce desired products.

Since the advent of fluidized solid systems for con- Verting chemicalreactants the designers have stressed development of simple andeffective methods and means for utilization of this principle, such asin the catalytic cracking of high-boiling hydrocarbons to usefulgasoline products. To achieve their objectives the designers have beenconstantly striving to develop simplified systems of high thermalefficiency which would provide them with maximum conversion ofhydrocarbon feeds to desired products. This has been accomplished to alarge extent by confining within a single unitary vessel an uppercontact chamber and a lower contact chamber, either one of which may beused as the hydrocarbon conversion zone or the regeneration zone withsuitable interconnecting transfer conduits between each chamber. Whilethese systems were a marked improvement over prior systems and werecommercially utilized, nevertheless these too have not been completelysatisfactory, particularly fromthe standpoint of conversion efiiciencyand product distribution.

As a result of an extensive investigation, many of the diflicultiesinherent in such designs have been overcome and consequently an improvedmethod and means is now available for commercial use.

An object of this invention, therefore, is to provide an improved methodand means for converting hydrocarbons in the presence of finely dividedcontact material.

Another object of this invention is to provide method and means forconverting high-boiling hydrocarbons to desired lower boilinghydrocarbons.

A still further object of this invention is to provide an improvedmethod and means for obtaining maximum conversion of high-boilinghydrocarbons to gasoline products.

Other objects and advantages of this invention will become apparent fromthe following description.

The present invention is directed to the method an means for contactinga hydrocarbon reactant with finely divided catalytic material underconversion conditions to suitable products in a plurality of conversionzones whereby the catalyst becomes contaminated with carbonaceousmaterial and volatile hydrocarbons. More specifically, in accordancewith the process of the present invention, freshly regenerated catalystis passed upwardly as a relatively dilute suspension at an elevatedtemperature above about 1000 F., or within a range of from about 1000 F.to about 1100 F., and at a velocity within the range of from about 30 toabout 60 feet per second, preferably from about 35 to about 45 feet persecond in contact with a vaporous hydrocarbon reactant. Accordingly, thehydrocarbon reactant will be in contact with the catalyst for a periodof time not greater than about 4 seconds and preferably less than 3seconds, for example, about 2 seconds, in its passage through the firstelongated confined conversion zone under elevated temperature crackingconditions to efiect the desired conversion of the hydrocarbonreactants. This upwardly flowing mixture of catalyst and hydrocarbons isdischarged from the upper portion of the first elongated conversion zoneinto a sec-. ond zone above the upper meniscus of a dense fluidized bedof catalytic material maintained in the lower portion of the secondzone. The second zone containing a dense fluid bed of contact materialtherein may be employed for the conversion of a more refractory feedmaterial such as a light cycle or a heavy cycle oil or a mixture of thetwo may be used therein. For example, a cycle oil may be employed toeffect controlled cooling of the catalyst prior to passing the catalystto the regeneration zone. The reaction products are separated from themajor portion of the entrained catalytic material in the first elongatedconversion zone by reducing the velocity of the vapors and by changingthe direction of flow of the suspension. That is the suspensionsvertical velocity component is changed such that the catalyst isdirected outwardly and settles downwardly onto the dense catalyst bed inthe second zone. During conversion of the hydrocarbon reactant thecatalyst becomes contaminated with volatile and non-volatile conversionproducts such as carbonaceous deposits. The thus contaminated catalystis separated from the more volatile products of reaction of the firstconversion in the enlarged settling zone above the dense bed of catalystin the second conversion zone and the catalyst falls into or onto thedense fluidized catalyst phase maintained in the second zone surroundingthe upper portion of the first conversion zone. In one embodiment ofthis invention, a second hydrocarbon reactant, either of the same ordifferent boiling range, generally higher boiling or more refractorythan that used in the first dilute phase conversion zone, such as acycle oil, is introduced either partially vaporized or as a liquid intothe lower portion of the second zone which is vaporized upon contactwith the catalyst and passes upwardly through the dense fluidizedcatalyst phase maintained in the second zone.

In the second zone or dense phase catalytic zone, the hydrocarbonreactant, generally cycle oil and any adsorbed hydrocarbons from thefirst high velocity conversion zone are subjected to cracking conditionswhich are lower in temperature than that employed in the first conversion zone, but for a much longer period of contact time. In the densephase catalytic conversion zone, the hydrocarbon reactant will be incontact with the catalyst forat least about 4 seconds and preferablyfrom about 4 to not more than about 10 seconds while employing acatalyst to oil ratio of from about 1 to about 20 to 1, and preferablyabout 10 to 1. Generally the temperature employed in the dense phaseconversion zone or second conversion zone will be much lower than thatin the first conversion zone and of the order of from about 900 F. toabout 960 F preferably about 925 F. Reaction prod ucts containingentrained catalyst of the first and second conversion zones areseparated from the major portion of the catalyst in the dilute phase orsettling zone in the upper portion of the second conversion zone. Theseproducts containing a minor portion of entrained catalyst are withdrawnfrom the upper portion of the second conversion zone and sent to asuitable cyclone separation zone wherein additional catalyst isseparated from the reaction products and returned to the bed of catalystin the stripping zone. The products of reaction, substantially free ofentrained catalyst are then sent to suitable recovery equipment forseparation into desired products. Catalyst contaminated with volatile orstrippable reaction products, as well as non-volatile carbonaceousdeposits is withdrawn from the dense phase of catalyst in the secondconversion zone and passed to a suitable stripping zone adjacent to thedense bed reaction zone and in open communication with the dilutecatalyst phase or settling zone above the dense bed of catalyst in thereaction zone. By

this arrangement the stripped products of reaction may be removed withthe remaining reaction products without any further extended contactwith catalyst. This is particularly desirable to avoid extended crackingof these products. Similarly, the catalyst separated in the cycloneseparator containing adsorbed products of reaction is passed to thestripping zone forthe recovery of these adsorbed products. The catalystis stripped of hydrocarbon products in the stripping zone with asuitable stripping gas, such as steam, which is passed upwardly througha descending relatively dense bed of catalyst in the stripping zone.Generally, the catalyst will be in contact with stripping gas for atleast about 30 seconds, and preferably from about 40 to about 60seconds. The stripped catalyst is passed downwardly as a relativelydense confined stream of catalyst from the bottom of the stripping zonethrough a standpipe to a regeneration zone positioned beneath the secondconversion zone and surrounding the lower portion of the firstconversion zone. In the regeneration zone carbonaceous materialcontaminating the catalyst as a result of the hydrocarbon conversionreactions is removed by burning in the presence of an oxygen-containinggas under controlled conditions to regenerate and heat the catalyst toconversion temperatures. The catalyst in the regeneration zone ismaintained in a relatively dense fluidized condition and theregeneration temperature is usually maintained within a range of fromabout 1000 F. to about 1250 F., preferably from about 1050 F. to about1150 F. The regenerated catalyst at an elevated temperature is strippedof regeneration gases with a suitable stripping gas such as steam orother inert gas in the lower portion of the regeneration zone as itpasses downwardly as an annular column of catalyst surrounding the inletto the transfer line cracking zone and the stripped catalyst is passedat an elevated temperature to the inlet of the first conversion zone forrecirculation through the system as hereinbefore described.

In the process of the present invention the reactors are positioned andinterconnected with respect to the regeneration zone to facilitatecirculation of catalyst at the desired temperature for each conversionstage and at a rate sufficiently high to provide the desired catalyst tooil ratio.

In one embodiment of this invention, all of the feed to be cranked,including fresh catalytic cracking feed material with or without recycleoil admixed therewith, is mixed with the hot freshly regeneratedcatalyst and passed upwardly through the elongated confined zone underelevated temperature conditions. As in the embodiment previouslydescribed, the cracking conditions employed in the elongated confinedzone are usually effected at an elevated temperature of from about 1000F., to about 1100" F., for a short period of time not to exceed about 4seconds. Thereafter the cracking reaction is stopped by immediatelyseparating the catalyst from the hydrocarbons and the separated catalystis caused to settle into a dense fluidized bed of catalyst materialsurrounding the upper portion of the reaction zone. In this specificembodiment, the catalyst in the dense fluidized bed is subjected to afirst stripping treatment and cooling of the catalyst to a desiredtemperature level is accomplished by the introduction of water thereto,that is to the lower portion of the fluid bed of catalyst. The water,upon introduction into the bed of catalyst is immediately vaporized andthe steam generated therefrom passes upwardly through the bed, therebystripping the catalyst of occluded reaction products and cooling thecatalyst to the desired temperature. A portion of the thus treatedcatalyst is continuously withdrawn from the first stripping stage andpassed to the adjacent stripping zone hereinbefore described, confinedwithin the upper chamber of the vessel wherein the catalyst is passeddownwardly in countercurrent contact with additional stripping gas priorto being passed to the regeneration zone. Accordingly, in this specificembodiment, more efficient and complete 4 stripping of the catalyst isachieved by virtue of the increased stripping time allotted thereo.

In another embodiment, it is within the scope of this invention toemploy more than one riser conduit, for example, a plurality of riserconduits, for contact of fresh feed material with hot freshlyregenerated catalyst. That is, at least two or more riser conduits ordilute phase conversion zones may be satisfactorily employed with thefresh feed material substantially equally distributed for passagethrough each zone with catalyst or the catalyst and feed passed to eachzone so selected as to provide a higher conversion temperature in onezone that the other, depending upon the particular conversiontemperature conditions desired. For example, one high velocityconversion zone may be maintained at a temperature within the range offrom about 1000 F. to about l050 F., with another maintained within therange of from about 1050 to about 1100 F., or any temperaturecombinations thereof.

In another embodiment of this invention the fresh feed to be cracked maybe separated into two or more fractions of different boiling range withcontact of each fraction under the most desirable temperature conversionconditions, as well as catalyst to oil ratio for each zone. That is theratio of catalyst to oil to be employed in the riser or transfer linecracking zone may vary from about 1 to about '20 to 1, or anyintermediate ratios thereof. By this novel arrangement of process stepsand apparatus for accomplishing the same, the refiner has at hisdisposal a highly flexible process and apparatus for the once throughhigh temperature-short contact time conversion of a hydrocarbon feedmaterial to desired products.

In the apparatus of this invention the regenerated finely dividedcontact material, which may be any suitable catalytic material, travelsupwardly through a riser or conversion conduit at a superficial linearvelocity of about 20 to about feet per second. At such velocities,provisions for decelerating the catalyst to insure separation ofcatalyst from conversion products must be provided. To accomplish thisseparation of the catalyst from the hydrocarbon products discharged fromthe riser or first transfer line conversion chamber or chambers, asuitable deflecting baflle is placed above and spaced apart from theoutlet of the riser to deflect the catalyst downwardly into the densecatalyst bed phase in the second conversion chamber. This deflectingbafile may be simply a horizontal plate, but is preferably a plate witha downwardly extending flange member or lip. In another embodiment theoutlet may be capped and a plurality of elongated slots placed aroundthe periphery at the discharge end of the riser conversion chamberthrough which the conversion products and catalyst are discharged fromthe first conversion chamber to the second or dense fluidized bedchamber. This latter arrangement may be referred to as a bird-cage. Inany event, the velocity component of the gases and catalyst dischargedfrom the first conversion chamber is sutficiently changed outwardly toseparate the major portion of the catalyst from the products bysettling, thereby causing the majority of the catalyst from the firstconversion chamber to settle into the dense fluidized catalyst bedmaintained in the second chamber. In the practice of the presentinvention, deceleration of the catalytic material in the dilute catalystphase above the dense catalyst phase to a superficial linear velocity ofabout 0.5 to about 3.0 feet per second, preferably about 1 to about 2.5feet per second, is usually the practice. This velocity correspondsgenerally to the velocity desired to minimize entrainment of catalystlines from the apparatus with the conversion products.

In addition to the above, the apparatus of this invention is confinedwithin a unitary vessel wherein the catalyst is passed generally insubstantially vertically confined paths thereby minimizing catalystattrition, as well as erosion of the equipment. The housing of theseparate and desired contact steps in the unitary vessel of thisinvention also has the added advantage of reducing the length ofnecessary transfer lines, as well as providing a process and apparatusof high thermal efficiency. These improvements are obviously of extremeimportance from an economic standpoint to the refiner.

The present invention is of particular significance and importance inthe art of refining hydrocarbons, since the quantity of catalyst in theconversion zones is held to a minimum and is generally less than thatemployed in the regeneration zone. Consequently and because of thismethod of operating the respective conversion zones, the conversionzones may be of substantially reduced crosssectional area with respectto the regenerator zone. Furthermore, by virtue of the carbon productionin catalytic cracking operations and the desire to maintain reasonablecatalytic activity, the system of the present invention in herentlyrequires substantially more catalyst in the regenerator than that in theconversion zones. In general, the present invention is particularlyapplicable to hydrocarbon conversion processes in which the regeneratorcontains from about 1.5 to about 6 times .as much catalyst on a weightbasis than the catalyst contained in the conversion zones, more usuallyabout 2 to 3 times on the same basis.

The apparatus to be used for the purpose of this invention contains inaddition to the conversion zones and regeneration zone, as hereinbeforediscussed, suitable means for withdrawal and stripping of catalystwithdrawn from the dense fluidized catalyst bed in the regeneration zoneprior to passing up the riser admixed With reactant. For this purpose, astripping Well open at its upper end is provided in the lower portion ofthe regeneration zone extending upwardly from the bottom thereof withthe wall of the well adjacent to the contaminated catalyst standpipebeing much higher than the remaining portion of the well wall. Theextension of the well wall adjacent to the contaminated catalyststandpipe minimizes tendency of spent or contaminated catalyst frompassing to the inlet of the first conversion zone before it has beenproperly regenerated. Furthermore, this well design takes advantage ofpressure developed in the bed of catalyst above it for the cyclic flowof catalyst in the system and the use of stripping gases thereinvirtually eliminates the passage of regeneration gases to the inlet ofthe first conversion zone. Generally the well may be from about 1 toabout 5 feet in height or from about 5 to 50 percent of the total heightof the regenerator. Another aspect of the apparatus design of thepresent invention is in the location of the regenerated catalystwithdrawal conduit or well. When only one riser conduit is employed, thewell and riser conduit will be preferentially coaxially positionedwithin the vessel. When employing two or more riser conduits, the wellfor each riser will be suitably positioned with respect to the standpipeto provide for uniform withdrawal of regeneration catalyst from thebeds. By carefully positioning the withdrawal well there is not only abetter circulation of the catalyst within the bed of the regenerator forcontact with regeneration gases, but there is a more uniform Withdrawalof regenerated catalyst from the catalytic bed. Hence the variousconduits will be symmetrically arranged in the regenerator to providefor the best circulation of catalyst particles in the bed. By thisarrangement, more uniform temperature distribution in the catalyst bedis obtained which virtually eliminates the formation of isolated smallhot portions of the catalyst in the bed.

Still another important apparatus feature of this invention resides inthe location of the stripping zone within the second conversion zone.This stripping zone is formed as a segmental well within and adjacent tothe second conversion zone which is formed by means of a verticaltransverse baflle extending from the bottom of conversion zone orreactor chamber to the upper portion thereof with suflicient space orarea for the stripping gas with entrained stripped products to passunrestricted into the upper portion of the conversion zone commonlyreferred to the dilute phase or settling zone. Such construction is notonly simple and economical, but lends itself for the desired withdrawalof contaminated catalyst from the second conversion zone, therebyminimizing the danger of forming stagnant portions of the catalyst inthe second conversion zone. Suitable slot Withdrawal means are providedin this baffle for withdrawal of contaminated catalyst from a desiredpredetermined level of the dense fluidized catalyst bed. Furthermore,the open upper end of the stripping zone in communication with thedilute phase of the second conversion zone permits passing strippedproducts directly to the dilute phase for combining with the reactionproducts and using a common cyclone separation system for removingcatalytic fines, thus providing additional apparatus economy.

The present invention is particularly applicable for catalyticallycracking high-boiling hydrocarbon either of the same or differentboiling range, for example, residual oils, reduced crudes, gas oils orfractions thereof. For example, when employing the improved process ofthe present nivention to contact fresh feed with freshly regeneratedcatalyst as a relatively dilute suspension in a riser or first highvelocity, high temperature conversion step and a recycle stock in asecond or dense fluidized catalytic conversion stage, quite often theamount of recycle stock returned to the reactor, together with slurrymaterial returned thereto may be substantially less than, equal to, oreven greater than the amount of fresh feed, depending upon the desiredheat balance of the system or process. Accordingly, the cooling effectof the recycle feed may be about the same or greater than the coolingeffect of the fresh feed stream so far as the catalyst is concerned.Therefore, with the regenerator operating at about 1150 F. and supplyingcatalyst at this temperature to the first cracking step, the mixture offresh feed and regenerated catalyst will be at least about 1000 F. andmay be as high as 1050 F., with the body of catalyst in the secondcracking zone held to a temperature below about 960 F. and preferablyabout 925 F. These temperatures, however, may be considerably altered,depending on the rate of catalyst circulation, feed preheat and catalystto oil ratio employed. Thus, in accordance with this invention, it isdesired to crack the fresh feed at a high temperature for a short periodof time with the recycle feed primarily for cooling the catalyst to adesired temperature level before returning the catalyst to theregeneration zone. The contact time between the hydrocarbon and thecatalyst in the first cracking zone will generally be less than 4seconds and of the order of from about 4 to about 1 second, preferablyfrom about 2 to about 3 seconds, whereas the contact time in the secondconversion zone will generally be greater than about 4 seconds and ofthe order of about 4 to about 10 seconds, preferably about 5 or 6seconds.

The catalyst employed in the process and apparatus of the presentinvention is usually a siliceous material which contains about 75 to 99percent silica with the remainder selected from any one or more of othersuitable materials, such as alumina, boria, magnesium, zirconia, etc.However, it is also within the purpose of the present invention to useother catalytic cracking materials either naturally occurring orsynthetically prepared.

The pressure employed within the vessel is usually low, for example, inthe order of about 1 atmosphere to about 50 p.s.i.g., more usually about5 to about 25 p.s.i.g. The weight space velocity measured as pounds ofoil charged to each reaction zone per pound of catalyst present thereinis usually of the order of about 0.25 to about 10, more usually about0.5 to 5. The relative ratio of catalyst to oil on a weight basis variesfrom about 2 to 30, generally the catalyst to oil ratio is about 5 to15, because it is desired to utilize the heat of combustion in theregeneration zone for the endothermic cracking reactions and to maintaina desired level of catalyst activity in each of the cracking zones.

As hereinbefore discussed, the catalyst, .as a result of the crackingreactions becomes contaminated with carbonaceous material which must beremoved by regeneration with an oxygencontaining gas, for example, air,at a temperature of from about 1000" F. to about 1200 F., more usuallyfrom about 1050 F. to about 1150 F., and at a pressure in the order ofabout 1 atmosphere to about 50 p.s.i.g.

The catalyst discharged from the first high velocity dilute phasereaction zone is separated from the reaction products as hereinbeforedescribed and passed directly to the second reaction zone containing arelatively dense phase fluidized catalyst bed without any intermediatestripping of the catalyst. The catalyst separated from the second densephase reaction zone is passed to the stripper as hereinbefore described.The contaminated catalyst is stripped at a temperature which isapproximately in the same range as the temperature employed in thesecond conversion zone. However, the stripping temperature may be variedas desired at any given time by employing a gasiform stripping agent ata higher or lower temperature. The gasiform stripping agent usuallyemployed is steam and may be either steam, hydrogen, a normally gaseoushydrocarbon, as for example methane, ethane, propane, etc., or mixturesthereof.

As can be seen by the drawing, the unitary vessel containing theseparate confined zones is in a substantially vertical position in orderthat the catalyst is circulated within the apparatus substantiallyvertically upwardly and downwardly. This particular arrangement not onlyreduces the length of transfer lines to a minimum thereby providing forhigh thermal efiiciency, but also the particular arrangement minimizescatalyst attrition, as well as erosion of transfer lines. In addition tothe above advantages, it is to be noted that the major proportion of thecatalyst riser which is employed as the dilute phase first cracking zoneis in indirect heat exchange with the regeneration zone.

In order to more specifically define the invention by way of example andto provide a better understanding thereof, reference is had to theaccompanying drawing, which is a diagrammatic illustration in elevationof an arrangement of apparatus used in accordance with this invention.

Referring to the drawing, a unitary vessel 2 is provided with an upperreaction zone 4 containing a dense fluidized bed of finely dividedcatalytic material having an upper level 60 and a lower regenerationzone 6 containing a dense fluidized bed of finely divided catalyticmaterial having an upper level or meniscus 28. Adjacent to the reactionzone, but confined within the vessel is a stripping zone 8 separatedfrom said reaction zone by a substantially vertical baffle 10 containinga plurality of catalyst transfer slots 12 for transferring contaminatedcatalyst from the reaction zone 4 into the stripping zone. The finelydivided catalytic material contaminated with carbonaceous material andvaporous reaction products is stripped of volatile products in thestripping zone by contact with a stripping gas such as steam introducedto the lower portion of the stripping zone by conduit 14 to a strippinggas distributor ring 16. The stripped finely divided catalytic materialis then passed downwardly as an elongated confined stream throughconduit 18 to the lower portion of the regeneration zone 6. The strippedcatalytic material is discharged from the bottom of conduit 18 through adischarge outlet 20. In order to control the rate of discharge ofcontaminated catalyst into the dense fluidized bed of catalyst in thereaction zone a suitable vertically movable plug valve 22 is providedfor insertion into the outlet 20 of the conduit 18. Suitableregeneration gas such as air is introduced by conduit 24 to the lowerportion of the regeneration zone and passes upwardly through a grid orperforated baffle 26 into the dense fluidized bed of catalyst toregenerate the catalytic material by burning of the carbonaceouscontaminant on the catalyst. Situated above the dense fluidizedcatalytic material in the regeneration zone is a relatively dilute phaseof catalyst mixed with flue gases. The flue gases containing entrainedcatalyst fines are passed through a two-stage cyclone separation systemidentified as cyclone separators 30 and 32 for removal of entrainedcatalyst fines from the flue gas prior to removing flue gases from theupper portion of the regenerator by conduit 34. The finely dividedcatalytic material separated from the flue gases in the cycloneseparators is then returned to the dense bed of catalytic material inthe regeneration zone by diplegs 36 and 38. Regenerated catalyticmaterial is separated from the dense bed of catalyst in the regenerationzone and passed downwardly into a circular well 40 defined by Wall 42.The regenerated catalyst is passed downwardly in well 40 countercurrentto stripping gas introduced to the bottom of the well by conduit 44 bystripping gas distributor ring 46. The use of stripping gas in the well40 not only reduces the tendency of regeneration gases from passing intothe well, but also prevents the hydrocarbon reactant from bypassing theriser inlet and upwardly through the well into the regeneration zone.Furthermore, the use of the stripping gas facilitates the transfer ofregenerated catalyst into the inlet of riser 56 by maintaining thecatalyst in a fluidized condition. The riser 56 of the present inventionfunctions not only as a means of transferring regenerated catalyst fromthe lower portion of the regeneration zone to the upper conversion zone4, but the riser is also used as a first stage high temperature-highvelocity cracking zone. That is to say a fresh hydrocarbon feed whichmay or may not be preheated to a temperature of about 800 F., admixedeither with or without steam is introduced by conduit 48 to hollow stemplug valve 52, which is vertically movable. In the event that steam ismixed with the hydrocarbon feed, the steam is introduced by conduit 50.In any event, the hydrocarbon feed introduced to hollow stem plug valve52, which is in alignment with the inlet 54 of riser conduit 56 picks upfinely divided regenerated catalyst at substantially the temperatureemployed in the regeneration zone and is passed as a relatively dilutesuspension of catalyst in oil upwardly through the reactor conduit 56 toa point above the upper level of the dense bed of catalyst maintained inthe reaction zone 4. The products of the first stage cracking whichtakes place in riser conduit 56 and entrained catalyst are deflected bybaflle 58 positioned above the outlet of the conduit in order tofacilitate separation of the reaction products from the catalyst. Thereaction products then enter the enlarged dilute catalyst phase settlingzone above the upper level 60 of the dense fluidized bed of catalyst inthe second conversion zone and pass to a suitable cyclone separator 62for the separation of any entrained finely divided catalyst from thereaction products. The reaction products, substantially free of finelydivided catalyst, are then removed from the upper portion of the reactorby conduit 64 and passed to suitable recovery equipment. The separatedfinely divided catalyst collected in cyclone separator 62 is returned bydipleg 66 to the dense phase bed 4 of catalytic material maintained inthe reactor. The catalytic material separated from the riser conversionstage settles into the dense fluidized bed of catalyst in conversionzone 4 to be used for the conversion of additional hydrocarbon feed inthe second conversion zone under less severe cracking conditions thanemployed in the first conversion zone. In conversion zone 4 anadditional hydrocarbon feed which may be of the same or differentboiling range than that employed in the first cracking stage andpreferably a cycle oil is introduced to the lower portion of the densefluidized bed by conduit 68 through a suitable distributor nozzle abovegrid 70. Steam or any inert gaseous material may be introduced below thegrid 70 by conduit 72 through a suitable distributor to assist influidizing the catalyst in the lower portion of the dense bed. Thehydrocarbon feed, either as a liquid or partially vaporized, is passedupwardly through the dense fluidized bed under less severe temperaturecracking conditions, but is held for a greater time of contact with thecatalyst than that employed in the first stage to convert the feed todesirable reaction products. Products of this second conversion stagepass into the dilute catalyst phase above the dense catalyst phase, arecommingled with the reaction products of the first conversion stage andremoved from the upper portion of the reactor as hereinbefore described.Contaminated catalyst is removed from the dense fluidized bed of thesecond conversion zone 4 by passing through a plurality of catalysttransfer slots 12 into the stripping zone for removal of hydrocarbonstherefrom with a suitable stripping gas as hereinbefore described.

It can be seen that the process and apparatus of the present inventionprovides numerous advantages over the prior art in that it enables theoperator to carry out two stages of cracking under different severityconditions as desired with a minimum of expensive apparatus and transferlines. These improvements in apparatus design and method of operationprovide a process of optimum versatility and economic advantage to theproducer. That is to say, by being able to control the severity ofcracking of the feed in each cracking stage, maximum conversion todesired products and optimum product distribution is obtainable.

EXAMPLE I The following data is presented by Way of example to showapplicants specific operating conditions for the process and apparatusof the present invention.

Summary of Forward Flow Cracking Results A. TRANSFER LINE CRACKINGReactor temp., F 1,000. Pressure 12 9 Catalyst to oil 10.6. W. r. w 52.430+cnv., vol. percent 45.6. Feed rate:

BPSD 16,000. Lbs/hr 210,000

Weight Vol. Percent Percent Yields:

1% d 11 111; ii id ry gas propane all g r. 4 6.98 1,117 BPSD. 0 -400 36.36 5,818 BPSD. Total cycle oil a 54.4 8,704 BPSD.

B. DENSE BED CRACKING Reactor temp, F 925. Pressur 12.9. Catalyst to oil(T.F. to dense bed) 24.6. W./hr./w. (basis T.F. to dense bed). 6.2.430+c0nv 66.5. Throughput ratio 1.5. Feed rate:

D 4,735. Lb./hr 63,200.

Weight Vol. Percent Percent 5,334 lb./hr. 4,146 lbjhr. 424 BPSD. 2,619BPSD. 1,444 BPSD. 142 BPSD.

It will be understood that numerous modifications of the presentinvention may be made without departing from the spirit thereof and thatthe precise details hereinbefore set forth in the example are purelyillustrative. For instance, the temperature in the first cracking stagemay be varied over a wide range as hereinbefore discussed or whenemploying a plurality of riser first conversion zones, diiferenttemperatures may be employed. It is to be noted, however, that thetemperature employed in the first cracking stage will be higher thanthat employed in the second cracking stage, and usually about 50 F.higher.

It is to be specifically noted that the amount of catalyst used in thesecond cracking stage will greatly exceed that employed in the firststage, since not only has the catalyst become partly deactivated by usein the first cracking stage, but the feed passed to the second stagewill be of the type which will require longer contact time with thecatalyst employed therein at the temperature employed in order to obtainthe desired degree of cracking of the feed. Therefore, the catalyst tooil ratio employed in the second cracking stage should be of the orderof from about 5 to about 50.

Having thus described my invention it should be understood that no unduelimitations or restrictions are to be imposed by reasons thereof.

I claim:

1. A hydrocarbon conversion process which comprises maintaining afluidized bed of finely subdivided solid catalyst particles in an upperreaction zone and a lower regeneration zone disposed in substantiallyvertical alignment, passing a first hydrocarbon reactant heavier thangasoline in contact with freshly regenerated catalyst withdrawn from thelower portion of the regeneration zone upwardly as a dilute suspensionthrough at least one elongated confined zone through said regenerationzone to a level above the bed of catalyst in said reaction zone, saidcontact between said first hydrocarbon reactant and said freshlyregenerated catalyst in said confined zones not to exceed a time greaterthan about four seconds, thereafter separating hydrocarbon conversionproducts of said first hydrocarbon reactant by separating catalyst fromsaid hydrocarbon substantially immediately upon discharge from saidelongated confined zone, passing a second hydrocarbon fraction morerefractory than said first hydrocarbon fraction upwardly through saiddense fluidized bed of catalyst in said reaction zone for a contact timenot less than about 3 seconds and at a lower temperature than employedin said dilute suspension contact step, withdrawing hydrocarbon productsof said first and second contact step from the upper portion of saidreaction zone, withdrawing contaminated catalyst from said reactionzone, stripping said withdrawn contaminated catalyst in a stripping zoneadjacent to said reaction zone with stripping gas for a period of timeof at least about 30 seconds, passing stripped products of reaction toabove the dense bed of catalyst in the reaction zone without passingtherethrough, and thereafter passing the stripped catalyst substantiallyvertically downwardly from the bottom of the stripping zone as anelongated confined stream to substantailly the bottom of the fluidizedbed of catalyst in the regeneration zone.

2. A method for converting hydrocarbon feed materials which comprisesmaintaining within a unitary vessel a dense fluidized bed of finelydivided catalytic material. in an upper reaction zone and a lowerregeneration zone, passing a first hydrocarbon feed material in contactwith freshly regenerated catalyst at a temperature of at least about1000 F. upwardly through at least one substantially vertical confinedconversion zone to above the upper level of the dense fluidized bed ofcatalyst in the reaction zone such that the contact time of the firsthydrocarbon reactant material with the catalyst will be less than about4 seconds whereby only a portion of said first hydrocarbon feed materialis selectively converted to desired products, thereafter immediatelyseparating the finely divided catalyst from the hydrocarbon of the firstconversion step and passing the separated catalyst to the densefluidized bed of catalyst in the reaction zone, passing a secondhydrocarbon fraction more refractory than said first hydrocarbonfraction upwardly through said dense catalyst bed under selectedconversion conditions including a contact time greater than about 3seconds, but not above about seconds, recovering products of said firstand second conversion steps from the upper portion of said reactionzone, withdrawing catalyst contaminated with products of reaction fromsaid reaction zone and passing the contaminated catalyst to an adjacentstripping zone, stripping catalyst in said stripping zone by passing thecontaminated catalyst downwardly and countercurrent to stripping gasintroduced to the lower portion of said stripping zone, passing strippedproducts of reaction to the upper portion of the reaction zone withoutpassing through the dense bed of catalyst therein, and passing strippedcatalyst from the bottom of the stripping zone substantially verticallydownwardly to the lower portion of the regeneration zone.

3. In a process for the cyclic circulation of finely divided catalystbetween a reaction zone and a regeneration zone wherein the process ismaintained in heat balance by the deposition of carbonaceous depositsupon the circulating catalyst and the carbonaceous deposits are removedfrom the catalyst by burning in a regeneration zone thereby heating thecatalyst to a desired elevated temperature, the improved method ofoperation whereby the conversion to desired products is increasedwithout upsetting the heat balance of the cyclic process which comprisespassing hot freshly regenerated catalyst withdrawn from the regenerationzone in admixture with a vaporous hydrocarbon reactant as a dilutesuspension through a first substantially vertical confined conversionzone at a temperature of about 1050" F. first in indirect heat exchangerelationship with the catalyst undergoing regeneration and then inindirect heat exchange relationship with a cooler dense fluidized bed ofcatalyst material at a temperature below about 960 F., separatingproducts of said first conversion zone from entrained catalyst,recovering separated products, passing catalyst separated from saidfirst conversion zone into the cooler dense fluid bed of catalyst,introducing a second liquid hydrocarbon stream more refractory than saidvaporous hydrocarbon reactant into said dense fluid catalyst bed wherebysaid bed is further substantially cooled, withdrawing cooled catalystfrom said dense fluid bed, stripping said withdrawn catalyst in astripping zone and passing stripped catalyst to the lower portion ofsaid regeneration zone as a substantially vertical downwardly flowingconfined column of catalyst.

4. A unitary apparatus comprising in combination an upper reactionchamber and a lower regeneration chamber, said upper reaction chamberhaving a substantially vertical transverse bafile member extendingupwardly from the bottom of the reaction chamber to the upper portionthereof thereby forming a separate stripping chamber adjacent to saidreaction chamber, a first open end standpipe extending substantiallyvertically downwardly from the bottom of the stripping chamber to abovea perforated grid horizontally positioned in the lower portion of theregeneration chamber, vertically movable plug valve aligned with thebottom open end of said standpipe, at least one cylindrical strippingwell chamber of smaller diameter than said regeneration chamberextending substantially vertically upwardly from the bottom of saidregeneration chamber, being open at its upper end and higher on the sideadjacent to said standpipe than the remaining portion of said well, eachof said chambers containing a relatively dense fluid bed of finelydivided contact material therein, a riser conduit extending from thelower portion of said cylindrical well substantially vertically upwardlyto above the bed of contact material in said reaction chamber, the upperend of said riser conduit adapted to change the direction of flow ofsaid contact material passing upwardly therein, a plug valve means forintroducing a first chemical reactant to the bot tom of said riserconduit, conduit means for passing a second chemical reactant to thelower portion of said bed of contact material in said reaction chamber,means for introducing a gaseous material beneath a perforated gridpositioned in the lower portion of said regeneration chamber for flow ofgaseous material upwardly into the bed of contact material in saidregeneration chamber, means for introducing stripping gas to the lowerportion of said stripping chambers, means for removing gaseous productfrom the upper portion of said regeneration chamber and means forremoving vaporous product from the upper portion of said reactionchamber.

5. A unitary apparatus comprising in combination an upper reactorchamber and a lower regeneration chamber, said reactor chamber being ofsmaller diameter than said regeneration chamber, each of said chamberscontaining a relatively dense fluidized bed of contact material therein,a separate stripping chamber confined within said reactor chamber andbeing in open vaprous communication in the upper portion therewith, astandpipe extending from the bottom of the stripping chamber to thelower portion of said regeneration chamber, a cylindrical strippingchamber higher on the side adjacent to said standpipe and open at itsupper end extending upwardly from the bottom of said regenerationchamber into the fluid bed of contact material therein, an open endriser conduit extending from the lower portion of the cylindricalstripping chamber substantially vertically upwardly to above the bed ofcontact material in said reactor chamber, the upper end of said riserconduit being provided with a plurality of elongated slots around thetop periphery thereof for the passage of finely divided contact materialtherethrough, a vertically movable hollow stem plug valve aligned withthe bottom open end of said riser conduit for the introduction of afirst hydrocarbon reactant thereto, a vertically movable plug valvealigned with the bottom of said standpipe, conduit means for introducinga second hydrocarbon reactant into the lower portion of the fluid bed ofcontact material in said reactor chamber, means for introducingstripping gas into the lower portion of each of said stripping chambers,means for introducing regeneration gas into the lower portion of saidregeneration chamber, means for removing a gaseous product from theupper portion of said regeneration chamber and means for removing avaporous product from the upper portion of said reactor chamber.

6. An apparatus comprising in combination an upper reactor chamber and alower regeneration chamber, each of said chambers containing arelatively dense fluidized bed of finely divided catalyst materialtherein, said regeneration chamber containing at least about twice thequantity of catalyst as employed in said reactor chamber, said reactorchamber provided with a separate stripping chamber by a vertical wallmember separating said stripping chamber from said reactor chamberterminating above the upper level of the dense bed of catalyst in saidreactor chamber and said wall member being provided with means forpassing catalyst from below the upper level of said dense fluidized bedin said reactor chamber to a more dense fluidized bed of catalyst insaid stripping chamber, said regeneration chamber provided with astripping chamber open at its upper end extending up wardly from thebottom of the regeneration chamber into the dense bed of catalysttherein, means for introducing stripping gas into the lower portion ofeach of said stripping chambers, an open end standpipe connected withthe bottom of the stripping chamber in the reactor chamber extendingsubstantially vertically downwardly to the lower portion of the densefluid bed of catalyst in the regeneration chamber and terminating belowthe upper level of the stripping chamber in said regeneration chamber, avertically movable plug valve aligned with the bottom open end of saidstandpipe, a riser conduit extending from the lower portion of thestripping chamber in said regeneration chamber substantially verticallyupwardly through said dense bed of catalyst in said reactor chamber toabove the upper bed level thereof, but below the terminus of the wallmember, said riser conduit adapted at its upper end thereof to alter thedirection of flow of finely divided catalyst passing upwardlytherethrough and distributing the catalyst on the top of the bed ofcatalyst in said reactor chamber, said riser conduit provided with avertically movable hollow stem plug valve for the introduction of avaporous material to the bottom of said riser conduit, conduit means forseparately introducing liquified material to the lower portion of saiddense fluid bed of catalyst in said reactor chamber, means for removinga vaprous material from the upper portion of said reactor chamber, meansfor introducing a gaseous material to the bottom of the bed of catalystin said regeneration chamber and means for removing a gaseous materialfrom the upper portion of said regeneration chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,459,824 Leifer Jan. 25, 1949 2,700,639 Weikart Jan. 25, 1955 2,727,810Lefier Dec. 20, 1955 2,883,332 Wickham Apr. 21, 1959 2,900,324 Patton etal. Aug. 18, 1959 2,953,520 Boisture Sept. 20, 1960

1. A HYDROCARBON CONVERSION PROCESS WHICH COMPRISES MAINTAINING AFLUIDIZED BED OF FINELY SUBDIVIDED SOLID CATALYST PARTICLES IN AN UPPERREACTION ZONE AND A LOWER REGENERATION ZONE DISPOSED IN SUBSTANTIALLYVERTICAL ALIGNMENT, PASSING A FIRST HYDROCARBON REACTANT HEAVIER THANGASOLINE IN CONTACT WITH FRESHLY REGENERATED CATALYST WITHDRAWN FROM THELOWER PORTION OF THE REGENERATION ZONE UPWARDLY AS A DILUTE SUSPENSIONTHROUGH AT LEAST ONE ELONGATED CONFINED ZONE THROUGH SAID REGENERATIONZONE TO A LEVEL ABOVE THE BED OF CATALYST IN SAID REACTION ZONE, SAIDCONTACT BETWEEN SAID FIRST HYDROCARBON REACTANT AND SAID FRESHLYREGENERATED CATALYST IN SAID CONFINED ZONES NOT TO EXCEED A TIME GREATERTHAN ABOUT FOUR SECONDS, THEREAFTER SEPARATING HYDROCARBON CONVERSIONPRODUCTS OF SAID FIRST HYDROCARBON REACTANT BY SEPARATING CATALYST FROMSAID HYDROCARBON SUBSTANTIALLY IMMEDIATELY UPON DISCHARGE FROM SAIDELONGATED CONFINED ZONE, PASSING A SECOND HYDROCARBON FRACTION MOREREFRACTORY THAN SAID FIRST HYDROCARBON FRACTION UPWARDLY THROUGH SAIDDENSE FLUIDIZED BED OF CATALYST IN SAID REACTION ZONE FOR A CONTACT TIMENOT LESS THAN ABOUT 3 SECONDS AND AT A LOWER TEMPERATURE THAN EMPLOYEDIN SAID DILUTE SUSPENSION CONTACT STEP, WITHDRAWING HYDROCARBON PRODUCTSOF SAID FIRST AND SECOND CONTACT STEP FROM THE UPPER PORTION OF SAIDREACTION ZONE, WITHDRAWING CONTAMINATED CATALYST FROM SAID REACTIONZONE, STRIPPING SAID WITHDRAWN CONTAMINATED CATALYST IN A STRIPPING ZONEADJACENT TO SAID REACTION ZONE WITH STRIPPING GAS FOR A PERIOD OF TIMEOF AT LEAST ABOUT 30 SECONDS, PASSING STRIPPED PRODUCTS OF REACTION TOABOVE THE DENSE BED OF CATALYST IN THE REACTION ZONE WITHOUT PASSINGTHERETHROUGH, AND THEREAFTER PASSING THE STRIPPED CATALYST SUBSTANTIALLYVERTICALLY DOWNWARDLY FROM THE BOTTOM OF THE STRIPPING ZONE AS ANELONGATED CONFINED STREAM TO SUBSTANTIALLY THE BOTTOM OF THE FLUIDIZEDBED OF CATALYST IN THE REGENERATION ZONE.